Dry grind ethanol production process and system with front end milling method

ABSTRACT

A dry grind ethanol production process and system with front end milling method is provided for improving alcohol and/or by-product yields, such as oil and/or protein yields. In one example, the process includes grinding corn kernels into particles then mixing the corn particles with a liquid to produce a slurry including oil, protein, starch, fiber, germ, and grit. Thereafter, the slurry is subjected to a front end milling method, which includes separating the slurry into a solids portion, including fiber, grit, and germ, and a liquid portion, including oil, protein, and starch, then milling the separated solids portion to reduce the size of the germ and grit and release bound starch, oil, and protein from the solids portion. The starch is converted to sugar, and alcohol is produced therefrom then recovered. Also, the fiber can be separated and recovered. Oil and protein may be separated and recovered as well.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/466,985, filed Mar. 24, 2011, and U.S. Provisional Application No.61/501,041, filed Jun. 24, 2011, the disclosures of which are herebyincorporated by reference herein in its entirety.

TECHNICAL FIELD

The present invention relates generally to dry mill alcohol productionand, more specifically, to improved milling methods and systems for drygrind ethanol plants to increase alcohol and/or by-product yields.

BACKGROUND

One alcohol of great interest today is ethanol. Most of the fuel ethanolin the United States is produced from a wet mill process or a dry grindethanol process. Although virtually any type and quality of grain can beused to produce ethanol, the feedstock for these processes is typicallycorn.

The conventional processes for producing various types of alcohol fromgrain generally follow similar procedures. Wet mill corn processingplants convert corn grain into several different co-products, such asgerm (for oil extraction), gluten feed (high fiber animal feed), glutenmeal (high protein animal feed), and starch-based products such asethanol, high fructose corn syrup, or food and industrial starch. Drygrind ethanol plants generally convert corn into two products, namelyethanol and distiller's grains with solubles. If sold as wet animalfeed, distiller's wet grains with solubles are referred to as DWGS. Ifdried for animal feed, distiller's dried grains with solubles arereferred to as DDGS. In the standard dry grind ethanol process, onebushel of corn yields approximately 8.2 kg (approximately 17 lbs.) ofDDGS in addition to the approximately 10.5 liters (approximately 2.8gal) of ethanol. This co-product provides a critical secondary revenuestream that offsets a portion of the overall ethanol production cost.

With respect to the dry grind process, FIG. 1 is a flow diagram of atypical dry grind ethanol production process 10. As a general referencepoint, the dry grind ethanol process 10 can be divided into a front endand a back end. The part of the process 10 that occurs prior todistillation and dehydration 24 is considered the “front end”, and thepart of the process 10 that occurs after distillation and dehydration 24(hereinafter “dehydration”) is considered the “back end”. To that end,the front end of the process 10 begins with a grinding step 12 in whichdried whole corn kernels are passed through hammer mills for grindinginto meal or a fine powder. The screen openings in the hammer millstypically are of a size 7/64, or about 2.78 mm, with the resultingparticle distribution yielding a very wide spread, bell type curve,which includes particle sizes as small as 45 micron and as large as 2 to3 mm.

The grinding step 12 is followed by a liquefaction step 16 whereat theground meal is mixed with cook water to create a slurry and a commercialenzyme called alpha-amylase is typically added (not shown). The pH isadjusted here to about 5.8 to 6 and the temperature maintained betweenabout 50° C. to 105° C. so as to convert the insoluble starch in theslurry to soluble starch. Various typical liquefaction processes, whichoccur at this liquefaction step 16, are discussed in more detail furtherbelow. The stream after the liquefaction step 16 has about 30% drysolids (DS) content with all the components contained in the cornkernels, including sugars, protein, fiber, starch, germ, grit, and oiland salts, for example. There generally are three types of solids in theliquefaction stream: fiber, germ, and grit, with all three solids havingabout the same particle size distribution.

The liquefaction step 16 is followed by a simultaneous saccharificationand fermentation step 18. This simultaneous step is referred to in theindustry as “Simultaneous Saccharification and Fermentation” (SSF). Insome commercial dry grind ethanol processes, saccharification andfermentation occur separately (not shown). Both individualsaccharification and SSF can take as long as about 50 to 60 hours.Fermentation converts the sugar to alcohol using a fermentor. Subsequentto the saccharification and fermentation step 18 is the distillation(and dehydration) step 24, which utilizes a still to recover thealcohol.

Finally, the back end of the process 10, which follows distillation 24,includes a centrifugation step 26, which involves centrifuging theresiduals, i.e., “whole stillage”, produced with the distillation step24 to separate the insoluble solids (“wet cake”) from the liquid (“thinstillage”). The “wet cake” includes fiber, of which there are threetypes: (1) pericarp, with average particle sizes typically about 1 mm to3 mm; (2) tricap, with average particle sizes about 500 micron; (3) andfine fiber, with average particle sizes of about 250 micron. The liquidfrom the centrifuge contains about 6% to 8% DS.

The thin stillage enters evaporators in an evaporation step 28 to boilaway moisture, leaving a thick syrup that contains the soluble(dissolved) solids from fermentation (25% to 40% dry solids). Theconcentrated slurry may be subjected to an optional oil recovery step 29whereat the slurry can be centrifuged to separate oil from the syrup.The oil can be sold as a separate high value product. The oil yield isnormally about 0.4 lb./bu of corn with high free fatty acids content.This oil yield recovers only about ¼ of the oil in the corn. Aboutone-half of the oil inside the corn kernel remains inside the germ afterthe distillation step 24, which cannot be separated in the typical drygrind process using centrifuges. The free fatty acids content, which iscreated when the oil is held in the fermenter for approximately 50hours, reduces the value of the oil. The (de-oil) centrifuge onlyremoves less than 50% because the protein and oil make an emulsion,which cannot be satisfactorily separated.

The centrifuged wet cake and the syrup, which has more than 10% oil, canbe mixed and the mixture may be sold to beef and dairy feedlots asDistillers Wet Grain with Soluble (DWGS). Alternatively, the syrup canbe mixed with the wet cake, then the concentrated syrup mixture may bedried in a drying step 30 and sold as Distillers Dried Grain withSoluble (DDGS) to dairy and beef feedlots. This DDGS has all the proteinand 75% of the oil in corn. But the value of DDGS is low due to the highpercentage of fiber, and in some cases the oil is a hindrance to animaldigestion.

Further with respect to the liquefaction step 16, FIG. 2 is a flowdiagram of various typical liquefaction processes that define theliquefaction step 16 in the dry grind ethanol production process 10.Again, the front end of the process 10 begins with a grinding step 12 inwhich dried whole corn kernels are passed through hammer mills forgrinding into meal or a fine powder. The grinding step 12 is followed bythe liquefaction step 16, which itself includes multiple steps as isdiscussed next.

Each of the various liquefaction processes generally begins with theground meal being mixed with cook, or back set, water, which can be sentfrom evaporation step 28 (FIG. 1), to create a slurry at slurry tank 32whereat a commercial enzyme called alpha-amylase is typically added (notshown). The pH is adjusted here, as is known in the art, to about 5.8 to6 and the temperature maintained between about 50° C. to 105° C. so asto allow for the enzyme activity to begin converting the insolublestarch in the slurry to soluble starch.

After the slurry tank 32, there are normally three optional pre-holdingtank steps, identified in FIG. 2 as systems A, B, and C, which may beselected depending generally upon the desired temperature and holdingtime of the slurry. With system A, the slurry from the slurry tank 32 issubjected to a jet cooking step 34 whereat the slurry is fed to a jetcooker, heated to 120° C., held in a U-tube for about 5 to 30 min., thenforwarded to a flash tank. The jet cooker creates a sheering force thatruptures the starch granules to aid the enzyme in reacting with thestarch inside the granule. With system B, the slurry is subjected to asecondary slurry tank step 36 whereat steam is injected directly to thesecondary slurry tank and the slurry is maintained at a temperature fromabout 90° C. to 100° C. for about 30 min to one hour. With system C, theslurry from the slurry tank 32 is subjected to a secondary slurrytank-no steam step 38, whereat the slurry from the slurry tank 32 issent to a secondary slurry tank, without any steam injection, andmaintained at a temperature of about 80° C. to 90° C. for 1 to 2 hours.Thereafter, the slurry from each of systems A, B, and C is forwarded, inseries, to first and second holding tanks 40 and 42 for a total holdingtime of about 2 to 4 hours at temperatures of about 80° C. to 90° C. tocomplete the liquefaction step 16, which then is followed by thesaccharification and fermentation step 18, along with the remainder ofthe process 10 of FIG. 1. While two holding tanks are shown here, itshould be understood that one holding tank or more than two holdingtanks may be utilized.

To increase the alcohol yield, and generate additional revenue, forexample, from oil and/or protein yields in the typical dry mill process,it would be beneficial to develop a process(es) to further break-up theinitially ground germ particles and grit particles, which include mostlystarch, to release more starch, oil, and/or protein therefrom. Such aprocess could provide for increased alcohol, oil, and/or protein yield,and produce much higher purity fiber (with less protein, starch andoil), which can be used as a raw feed stock for the paper industry andcellulosic to secondary alcohol processes.

Various dry grind systems have attempted to increase alcohol yields, forexample, by focusing on the grinding aspect in the dry grind process 10.However, such systems are known not to have produced very good results.For example, with the grind systems in today's market, these systemstend to decrease the size on all of the particles (fiber, germ, andgrit) at the same time and at the same rate. The resulting corncomponents can be difficult to separate, particularly if all of theparticles, including the fiber, are ground too small, e.g., less than300 microns. While alcohol yield may improve with smaller particlesizes, this can also produce a very wet decanter cake and dirtyoverflow, i.e., dirty thin stillage. And this dirty overflow can createfouling and result in lower syrup concentrations during the evaporationstep 28. Lower syrup concentrations and wetter cakes also produceincreased dryer loads raising the drying costs of DDGS. In contrast, ifthe resulting corn components are too large in size, e.g., greater than1000 microns, the particles will not adequately convert to sugar duringthe liquefaction step 16 and alcohol yield, for example, will drop.

Such conventional systems also tend to focus on either grinding theentire stream or a partially separated stream in a very wet slurry form,without any dewatering prior to grinding. For grinding solid particles,the feed that is sent to the grind mill should be as dry as possible toyield maximum grinding results. Current systems also have failed toremove fine solid particle before feeding the particles to thecutting/grinding device. As such, the fine solid particles becomesmaller particles, i.e., too small, creating problems on the back end ofthe process by producing very wet cakes and dirty overflow, as discussedabove.

It would thus be beneficial to provide an improved milling method(s) andsystem(s) for dry grind ethanol plants that can improve alcohol, oil,and/or protein yields, and generate additional revenue from oil and/orprotein yields, for example, while avoiding and/or overcoming theaforementioned drawbacks.

SUMMARY

The present invention relates to to improved milling methods and systemsfor dry grind ethanol plants to increase alcohol and/or by-productyields. Such improved milling method(s) and system(s) for dry grindethanol plants can improve alcohol, oil, and/or protein yields, andgenerate additional revenue from oil and/or protein yields.

In one embodiment, a dry grind ethanol production process is provided,which includes grinding corn kernels into particles then mixing the cornparticles with a liquid to produce a slurry including oil, protein,starch, fiber, germ, and grit. Thereafter, the slurry is subjected to afront end milling method, which includes separating the slurry into asolids portion, including fiber, grit, and germ, and a liquid portion,including oil, protein, and starch, then milling the separated solidsportion to reduce the size of the germ and grit and release boundstarch, oil, and protein from the solids portion. The starch isconverted to sugar, and alcohol is produced therefrom then recovered.Also, the fiber can be separated and recovered, and oil and protein maybe separated and recovered as well.

In another embodiment, a dry grind ethanol production process isprovided, which includes grinding corn kernels into corn particles, thenmixing the corn particles with a liquid to form a slurry. Thereafter, anamount of the liquid is reduced from the slurry to form a wet cake thenthe wet cake is milled. Alcohol, fiber, oil and protein can be separatedand recovered in this process as well.

In yet another embodiment, a system for dry grind ethanol production isprovided, which includes a grinding device, which grinds corn kernelsinto particles and a slurry tank in which the corn particles mix with aliquid to produce a slurry including oil, protein, starch, fiber, germ,and grit. The system further includes a first dewatering device, whichseparates the slurry into a solids portion, including fiber, grit, andgerm, and a liquid portion, including oil, protein, and starch. A sizereduction device, which follows the first dewatering device, reduces thesize of the germ and grit of the solids portion and releases boundstarch, oil, and protein from the solids portion. And at least oneholding tank, which aids in converting the starch to sugar is provided.The system further includes a fermentor to produce alcohol from thesugar and a still to recover the alcohol as well as a second dewateringdevice, which separates and recovers the fiber.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the invention and,with a detailed description of the embodiments given below, serve toexplain the principles of the invention.

FIG. 1 is a flow diagram of a typical dry grind ethanol productionprocess;

FIG. 2 is flow diagram of various typical liquefaction processes thatdefine the liquefaction step in a dry grind ethanol production process;

FIG. 3 is a flow diagram showing a dry grind ethanol production processand system with front end milling method in accordance with anembodiment of the invention;

FIG. 3A is a simplified flow diagram of the dry grind ethanol productionprocess and system of FIG. 3;

FIGS. 3B-3D are simplified flow diagrams showing a variation of the drygrind ethanol production process and system with front end millingmethod of FIG. 3A in accordance with embodiments of the invention;

FIG. 4 is a flow diagram showing a dry grind ethanol production processand system with front end milling method in accordance with anotherembodiment of the invention;

FIG. 5 is a flow diagram showing a dry grind ethanol production processand system with front end milling method in accordance with anotherembodiment of the invention;

FIG. 6 is a flow diagram showing a dry grind ethanol production processand system with front end milling method in accordance with anotherembodiment of the invention;

FIG. 7 is a flow diagram showing a dry grind ethanol production processand system with front end milling method in accordance with anotherembodiment of the invention;

FIG. 7A is a flow diagram showing a variation of the dry grind ethanolproduction process and system with front end milling method of FIG. 7 inaccordance with an embodiment of the invention;

FIG. 7B is a flow diagram showing a variation of the dry grind ethanolproduction process and system with front end milling method of FIG. 7Ain accordance with an embodiment of the invention;

FIG. 8 is a flow diagram showing a dry grind ethanol production processand system with front end milling method in accordance with anotherembodiment of the invention;

FIG. 9 is a flow diagram showing a dry grind ethanol production processand system with front end milling method in accordance with anotherembodiment of the invention;

FIG. 9A is flow diagram showing a variation of the dry grind ethanolproduction process and system with front end milling method of FIG. 9 inaccordance with another embodiment of the invention; and

FIG. 9B is flow diagram showing a variation of the dry grind ethanolproduction process and system with front milling method of FIG. 9A inaccordance with another embodiment of this invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

FIGS. 1 and 2 have been discussed above and represent a flow diagram ofa typical dry grind ethanol production process and various typicalliquefaction processes that define the liquefaction step in a dry grindethanol production process, respectively.

FIGS. 3-9B illustrate various embodiments of a dry grind ethanolproduction process and system with front end milling method forimproving alcohol, oil and/or protein yields, and for producing a purer,more desirable fiber for secondary alcohol production, for example.These processes and systems are discussed in detail herein below.

With reference first to FIG. 3, this figure depicts a flow diagram of anembodiment of a dry grind ethanol production process and system with afront end milling method for improving alcohol and/or byproduct yields,e.g., oil and/or protein yields. In this process 100, corn is firstsubjected to a grinding step 102, which involves use of a hammer mill,or the like, to grind corn to particle sizes less than about 7/64 inchand allow for the release of oil therefrom. In one example, the screensize for separating the particles can decrease from about 7/64 inch toabout 6/64 inch. In another example, the particle sizes are from about50 micron to 3 mm. The grinding helps break up the bonds between thefiber, protein, starch, and germ.

Next, the ground corn flour is mixed with water, referred to as cookwater, at slurry tank 104 to create a slurry and begin liquefaction. Anenzyme(s), such as alpha amylase, optionally can be added to the slurrytank 104. The slurry may be heated at the slurry tank 104 to about 150°F. to about 200° F. for about 30 minutes to about 120 minutes. Thestream from the slurry tank 104 contains about 1 lb/bu free oil andabout 1.5 lb/bu germ (particle size ranges from about 50 micron to about3 mm), 1.8 lb/bu grit (particle size ranges from about 50 micron toabout 3 mm), and 4.2 lb/bu fiber (particle size ranges from about 50micron to about 3 mm).

The feed from the slurry tank 104 is next subjected to a liquid/solidseparation step 106, which defines the beginning of the front endmilling method. While the front end milling method begins after theslurry tank 104 in FIG. 3, it should be understood that it may situatedat any location along the liquefaction process, including from theslurry tank 104 up to fermentation step 111. The liquid/solid separationstep 106 separates a generally liquefied solution (about 60-80% byvolume), which includes free oil, protein, and fine solids (which do notneed grinding), from heavy solids cake (about 20-40% by volume), whichincludes the heavier fiber, grit, and germ, which can include bound oil,protein, and/or starch. The liquid/solid separation step 106 usesdewatering equipment, e.g., a paddle screen, a vibration screen, screendecanter centrifuge or conic screen centrifuge, a pressure screen, apreconcentrator, and the like, to accomplish separation of the solidsfrom the liquid portion. The fine solids are no greater than 200microns. In another example, the fine solids are no greater than 500microns, which is generally dependent upon the screen size openings usedin the liquid/solid separation device(s).

In one example, the dewatering equipment is a paddle screen, whichincludes a stationary cylinder screen with a high speed paddle withrake. The number of paddles on the paddle screen can be in the range of1 paddle per 4 to 8 inches of screen diameter. In another example, thedewatering equipment is a preconcentrator, which includes a stationarycylinder screen with a low speed screw conveyor. The conveyor pitch onthe preconcentrator can be about ⅙ to ½ of the screen diameter. Thenumber of paddles on the paddle screen and the conveyor pitch on thepreconcentrator can be modified depending on the amount of solids in thefeed. The gap between the paddle screen and paddle can range from about0.04 to 0.2 inch. A smaller gap gives a drier cake with higher capacityand purer fiber but loses more fiber to filtrate. A larger gap gives awetter cake with lower capacity and purer liquid (less insoluble solid).The paddle speed can range from 400 to 1200 RPM. In another example, thepaddle speed can range from 800 to 900 RPM. A higher speed provideshigher capacity but consumes more power. One suitable type of paddlescreen is the FQ-PS32 paddle screen, which is available from Fluid-Quip,Inc. of Springfield, Ohio.

The screen for the dewatering equipment can include a wedge wire typewith slot opening, or a round hole, thin plate screen. The round holescreen can help prevent long fine fiber from going through the screenbetter than the wedge wire slot opening, but the round hole capacity islower, so more equipment may be required if using round hole screens.The size of the screen openings can range from about 45 micron to 500micron. In another example, the screen openings can range from 100 to300 micron. In yet another example, the screen openings can range from200 to 250 microns. Smaller screen openings tend to increase theprotein/oil/alcohol yield with higher equipment and operation cost,whereas larger screen openings tend to lower protein/oil/alcohol yieldwith less equipment and operation cost.

The now separated liquefied starch solution can be subjected to anoptional oil separation step 108, which can use any type of oilseparator, such as a mud centrifuge, three phase decanter, discdecanter, three phase disc centrifuge, and the like, to separate oilfrom the liquefied starch solution by taking advantage of densitydifferences. In particular, the liquefied starch solution is used asheavy media liquid to float oil/emulsion/fine germ particle. Theliquefied starch solution has densities of about 1.1 to 1.2 grams/cc and0.9 to 0.92 grams/cc for oil and 1 to 1.05 grams/cc for germ.

There can be three phases discharged from the oil separation step 108.The first is a light phase, which includes oil or an oil/emulsion layer.The second is a heavy phase, which includes the liquefied starchsolution, possibly with some small germ particles. The third phase isthe solid phase, which contains fine fiber, grit particle, and starch.The underflow heavy phase and solid phase can be combined as isillustrated in FIG. 3; otherwise, they can remain separated and sent todifferent locations for optimizing results.

The oil/emulsion/fine germ layer can be forwarded to an oil polish step109 whereat the layer can be subjected to centrifugation, including athree phase decanter, three phase disc centrifuge, or the like toseparate pure oil from the emulsion and fine germ particle. From the oilpolish step 109, the emulsion and fine germ particle can be dischargedas a heavy phase and optionally subjected to a solvent extraction step110 to recover additional oil, or returned to join up with the combinedstarch solution/heavy phase from the oil separation step 108. At the oilpolish step 109, alcohol, such as 200 proof alcohol from a distillationtower from distillation step 118, can be added to the emulsion and finegerm particles so as to break the emulsion and extract oil from the finegerm particle, which normally are less than 100 micron. The remainingfine germ particles then are sent on to fermentation step 111, asindicated.

The oil that is recovered at step 110 has a much more desirable qualityin terms of color and free fatty acid content (less than 7% and, inanother example, less than 5%) as compared to oil that is recovereddownstream, particularly oil recovered after fermentation 111. Inparticular, the color of the pre-fermentation recovered oil is lighterin color and lower in free fatty acid content. The oil yield at step 108can reach about 0.9 lb/bu whereas current oil recovery from evaporatorstreams average below 0.5 lb/bu. With the oil polish step 109 andsolvent extraction step 110, the oil yield can increase to as high as1.4 lb/bu.

Returning now to the liquid/solid separation step 106, the wet cake ordewatered solids portion of the stream at the liquid/solid separationstep 106 (about 60 to 65% water) continues along the front end millingmethod and is next subjected to a dewatered milling step 112, whereatthe solids, particularly the germ and grit, are reduced in size via sizereduction equipment. The size reduction equipment can include a hammermill, a pin or impact mill, a grind mill, and the like. In one example,the size reduction equipment is a pin mill or grind mill. This dewateredmilling step 112 is intended to break the germ and grit particles andthe bonds between fiber and starch, as well as oil and protein, withoutcutting the fiber too fine, thereby giving sharper separation betweenthe fiber and protein/starch/oil.

In a dewatered form, the germ and grit particles are able to break apartmore easily than the fiber as a result of increased rubbing action inwhich less fine fiber is created, but the germ and grit are more fullymilled. This results in a relatively non-uniform particle size amongstthe milled solids. For example, germ and grit particles can be milled toa particle size between about 300 to 800 microns, whereas a majority ofthe fiber remains within a particle size range of 500 to 2000 micron. Inone example, greater than 75% of the fiber remains within a particlesize range of 500 to 2000 micron. In another example, no greater than80% by weight of the total particles after the dewatered milling step112 have a particle size less than 800 microns. In another example, nogreater than 75% by weight of the total particles after the dewateredmilling step 112 have a particle size less than 800 microns. In stillanother example, no greater than 65% by weight of the total particlesafter the dewatered milling step 112 have a particle size less than 800microns. In another example, about 30% to about 50% by weight of thetotal particles after the dewatered milling step 112 have a particlesize from about 100 microns to about 800 microns. In still anotherexample, about 40% to about 50% by weight of the total particles afterthe dewatered milling step 112 have a particle size from about 100microns to about 800 microns. In yet another example, no greater than50% by weight of the total particles after the dewatered milling step112 have a particle size from about 100 microns to about 800 microns.The % protein in the solid particles that are larger than 300 micron isabout 29.5%. After grind and if washing techniques are utilized, the %protein in fiber can decrease from about 29.5% to about 21.1%. The % oilin fiber can decrease from about 9.6% to about 6.4%, and the % starch infiber can decrease from about 5.5% to about 3%.

If a grind mill is used for particle size reduction at the dewateredmilling step 112, the design of the grind plates (not shown) for thegrind mill can be varied to accomplish the germ and grit grinding, whiletending to avoid fiber grinding. Historically, the grind plates, whichare in generally opposing fashion, typically define a group of about 6grind plate segments that form an annular ring when combined togetherand secured to the surface of a grind disc. Each grind plate segmentand, consequently the grind plate itself, contains “tooth” designsplaced in rows of annular rings or bars of various widths that extendfrom the inside diameter to the outside diameter of the grind plate.With bar type design grind plates, the width and depth can be varied toprovide more effective grinding of the germ and grit, while tending toavoid the fiber. In one example, the bar is 20 inches long. Differentcombinations, numbers, and shapes and sizes of “teeth” or bar designsmay be provided to more effectively grind the germ and grit, whiletending to avoid the fiber. Also, the gap between the grind plates aswell as the RPMs can be adjusted for desired performance and energyefficiency. In one example, the gap can be from 0.01 to 0.3 inch. Inanother example, the plate gap is about 0.020 to 0.15 inch. Also, in oneexample, the RPM can be from 900 to 3000 for one or more grind plates.In another example, the RPM is about 1800.

The grind plate may be composed of white iron, which has high abrasionresistance with approximately 25% chrome content to increase corrosionresistance, but can be formed of any suitable metal or alloy, plastic,composite, and the like. Also the teeth size (width, height, andlength), shape of the teeth, distance between teeth, and number of teethon each row can vary to accomplish desirable germ and grit grinding,while tending to avoid fiber grinding.

One type of grind mill having a suitable type of grind plate is theFQ-136 grind mill, which is available from Fluid-Quip, Inc. ofSpringfield, Ohio. This type of grind mill has one 36″ inch diameterstationary disc and one 36″ inch diameter rotating disc. Grind platesegments defining the grind plate are installed onto each disc, and thegap between the two discs can be varied to produce an effective grindresult. Grind mills can be made with larger or smaller diameter discs.The FQ-152 grind mill also available from Fluid-Quip, Inc. ofSpringfield, Ohio, has 52″ inch diameter discs. Larger diameter discscan provide higher tangential velocity at the outside edge of the discsas compared to smaller discs, which can provide more impact and grindingor shear effect if run at the same rotational speeds. Grind mills canalso be made with two rotating discs, which can vary in diameter. Inthis case, the discs rotate in opposite directions, producing a neteffective disc to disc speed twice that of a single rotating disc.Increased speed will increase the number of teeth or bar crossings whichwill effect impact and/or shear effect on the medium passing through thegrind mill.

If a pin/impact mill is used for particle size reduction, different pinsizes and types, e.g., round, triangular, hexagonal, and the like, canbe used depending on operation requirements to optimize the dewateredmilling step 112. In one example, the pin sizes can include round pins,which can be approximately 2⅛ inches in height and 1⅝ inches indiameter. Also, the RPM for the pin/impact mill can be from 2000 to3000. The pins can be made of stainless steel or other suitablecorrosion resistant metal or metal alloy, plastic, composite, and thelike. One suitable type of pin/impact mill, which uses an impact forceto help break the germ and grit, while tending to avoid fiber grinding,is the FQ-IM40, which is available from Fluid-Quip, Inc. of Springfield,Ohio.

After milling, which itself defines the end of the front end millingmethod, the solids can be mixed with the liquefied starch solution fromeither the optional oil separation step 108 or from the liquid/solidseparation step 106, as shown, to form a heavy slurry then subjected toone of three optional pre-holding tank systems at pre-holding tank step113, i.e., generally one of systems A, B, and C of FIG. 2. Also, if theemulsion and fine germ particle from the oil polish step 109 are notoptionally subjected to the solvent extraction step 110, the underflow(mainly liquefied starch) is joined up with the underflow solution fromthe oil separation step 108, which is joined up with the solids from thedewatered milling step 112 to form the heavy slurry, and sent to thepre-holding tank step 113.

At pre-holding tank step 113 and as generally discussed above withrespect to FIG. 2, the heavy slurry can be subjected to system A or apressurized jet cooker and heated to about 101° C. to about 130° C. forabout 3 to 30 minutes under a pressure of about 20 psi to about 150 psi,held in a U-tube for about 5 to 15 min., then forwarded to a flash tankand maintained at a temperature above 95° C. for about 3 to 30 minutesto help solubilize the starch. Alternatively, the heavy slurry can besubjected to system B or fed to a secondary slurry tank whereat steam isinjected directly to the secondary slurry tank and the slurry ismaintained at a temperature from about 95° C. for about 60 to 120minutes. Alternatively, the heavy slurry can also be subjected to systemC or fed to a secondary slurry tank, without steam injection, andmaintained at a temperature of about 60° C. to 85° C. for 1 to 4 hours.

Thereafter, the slurry from the pre-holding tank step 113 is forwarded,in series, to first and second holding tanks 114 and 115 for a totalholding time of about 2 to 4 hours at temperatures of about 60° C. to85° C. to further solubilize the starch component in the slurry streamand complete liquefaction before sending to fermentation step 111. Whiletwo holding tanks are shown here, it should be understood that oneholding tank or more than two holding tanks may be utilized.

Various enzymes (and types thereof) such as amylase or glucoamylase,fungal, cellulose, cellobiose, protease, and the like can be optionallyadded during and/or after the dewatered milling step 112, pre-holdingtank step 113, or the holding tanks 114 and 115 to enhance theseparation of components, such as to help break the bonds betweenprotein, starch, and fiber.

After the second holding tank 115, the stream from the optional solventextraction step 110 can be joined up with the liquefied starch slurrysolution and sent to fermentation step 111 whereat fermentation occurs.

As compared with current dry milling processes, the front end millingmethod, which includes the liquid/solid separation step 106 and thedewatered milling step 112, gives a more complete starch conversion. Inaddition, an increase of about 1.0% alcohol yield, about 0.05 lb/bu oilyield, and 0.3 lb/bu protein yield can be realized.

The liquefied starch solution at fermentation step 111, which nowincludes the fiber, reduced grit and germ particles, as well as proteinand oil, is subjected to fermentation to convert the sugar to alcohol,followed by a distillation step 118, which recovers the alcohol. At thedistillation step 118, the fermented solution (normally referred to hereas “beer”) is separated from the whole stillage, which includes fiber,protein, oil, and germ and grit particles, to produce the alcohol. Thealcohol yield is about 2.78 gal/bu, which is an increase of about 1%over conventional yields, due at least in part to the dewatered millingstep 112 whereat starch in the grit and germ particle is released andeventually converted to sugar to produce more alcohol.

With continuing reference to FIG. 3, the back end of the process 100,which itself is optional insofar as a typical back end process may beutilized here, may include a whole stillage separation step 120 whereatdewatering equipment, e.g., a paddle screen, vibration screen,filtration centrifuge, pressure screen, screen bowl decanter and thelike, is used to accomplish separation of the insoluble solids or “wholestillage”, which includes fiber, from the liquid “thin stillage”portion. The screen openings can range in size here from about 45 to 400micron, depending upon the purity of fiber and protein desired here. Inone example, the screen of the dewatering equipment has openings of asize from about 75 to 800 micron. And, in another example, the size ofthe openings range from about 150 to 500 micron.

The thin stillage from the whole stillage separation step 120 may besent to a protein recovery step 122, which uses, for example, adecanter, a nozzle centrifuge, or a disc decanter to recover fine germand protein (corn gluten as well as spent yeast). These recoveredcomponents are sent to a drying step 124, which utilizes a dryer, suchas a rotary or ring dryer, to yield a gluten/germ mix (protein meal).

The insoluble solids (whole stillage), or the wet cake fiber portion,from the whole stillage separation step 120 is sent to a washing anddewatering step 126, which utilizes a filtration device, such as a fibercentrifuge, to separate the different fiber types by relying on ascreen(s) having different sized openings. One exemplary filtrationdevice for the wet cake washing and dewatering step 126 is shown anddescribed in Lee U.S. Patent Application Publication No. 2010/0012596,the contents of which are incorporated herein by reference. The screenopenings for the fiber centrifuge normally will be about 500 microns tocapture amounts of tip cap, pericarp, as well as fine fiber, but canrange from about 400 micron to about 1500 micron. Residual liquid fromthe centrifuge can join back up with the thin stillage prior to theprotein recovery step 122. The centrifuged fiber contains less than 3%starch as compared with normal dry mill fiber, which has 4 to 6% starchin fiber. The % protein in the fiber also decreases from a conventional29% to 21% and the % oil decreases from a conventional 9% to about 6%.

The overflow stream from the protein recovery step 122 can move to afine protein recovery step 130, which uses, for example, a clarifierfollowed by a high speed decanter or disc decanter, and the like, toseparate the liquid portion of the stream, which includes oil, from theremaining heavier components, including residual protein. Thecentrifuged protein then is sent to drying step 124, along with therecovered protein from the protein recovery step 122, to yield thegluten/germ mix (protein meal), which has about 50% protein. The totalprotein yield from the process is more than 4 lb./bu.

The liquid overflow from the fine protein recovery step 130 moves toevaporators in an evaporation step 136 so as to separate any oiltherefrom by boiling away moisture, leaving a thick syrup. The highconcentrated syrup (more than 60% DS) can be used, amongst other things,as (a) nutrition for secondary alcohol production, (b) animal feedstock, (c) plant food, (d) and/or anaerobic digestion to produce biogas.The concentrated slurry optionally can be sent to a centrifuge, forexample, to separate the oil from the syrup. The oil can be sold as aseparate high value product.

The syrup can be mixed with centrifuged wet cake from washing anddewatering step 126, and the mixture may be sold to beef and dairyfeedlots as Distillers Wet Grain with Soluble (DWGS). The wet cake andconcentrated syrup mixture also optionally may be dried in a drying step140 and sold as Distillers Dried Grain with Soluble (DDGS) to dairy andbeef feedlots. This DDGS has less than 25% protein and 8% oil.

With reference now to FIG. 3A, this figure depicts a simplified flowdiagram of the dry grind ethanol production process and system 100 ofFIG. 3, and particularly the front end milling method, which includes inits simplest form liquid/solid separation step 106 and dewatered millingstep 112. As is discussed in detail below, more than one liquid/solidseparation step 106 and dewatered milling step 112 may be utilized here,for example, for alcohol, oil, protein, and/or fiber production, withdesirable yields and/or purity.

With continuing reference to FIG. 3A, to accomplish this desirablealcohol, oil, protein, and/or fiber production, corn first is ground toparticle sizes less than about 7/64 inch. The grinding helps break upthe bonds between the fiber, protein, starch, and germ and allows forthe release of oil from the corn. The ground corn flour is mixed withcook water at slurry tank 104 to create a slurry and begin liquefaction.An enzyme(s), such as alpha amylase, optionally can be added to theslurry tank 104 to assist in converting insoluble starch in the slurryto soluble starch. The stream from the slurry tank 104, which contains,e.g., sugars, protein, oil, germ particle (particle size ranges fromabout 50 micron to about 3 mm), grit (particle size ranges from about 50micron to about 3 mm), and fiber (particle size ranges from about 50micron to about 3 mm), is forwarded to the liquid/solid separation step106. The liquid/solid separation step 106, which again defines thebeginning of the front end milling method, separates a generallyliquefied solution (about 60-80% by volume), which includes oil,protein, and fine solids (which do not need grinding), from heavy solidscake (about 20 to 40% by volume), which includes the heavier fiber,grit, and germ. The oil in the liquid portion optionally may besubjected to a front end oil separation step 108 to recover the free oilin the stream.

The dewatered solids portion of the stream (about 60 to 65% water) issubjected to the dewatered milling step 112, which defines the end ofthe front end milling method. Here, the solids, particularly the germand grit, are reduced in size via size reduction equipment, which breaksthe germ and grit particles and the bonds between fiber and starch, aswell as oil and protein, without cutting the fiber too fine, therebygiving sharper separation between the fiber and protein/starch/oil. Thegerm and grit particles are milled to a particle size between about 300to 800 microns, whereas a majority of the fiber remains within aparticle size range of 500 to 2000 micron. Various enzymes (and typesthereof) such as amylase or glucoamylase, fungal, cellulose, cellobiose,protease, and the like can be optionally added to enhance the separationof components, such as to help break the bonds between protein, starch,and fiber. The heavy slurry from the dewatered milling step 112 issubjected to pre-holding tank step 113 followed by first and secondholding tanks 114 and 115 to further solubilize the starch component inthe slurry stream and complete liquefaction before sending tofermentation step 111. Thereafter, alcohol and optionally fiber, oil,and/or protein are recovered from the process 100.

With reference now to FIGS. 3B-3D, these figures depict a simplifiedflow diagram showing variations of the dry grind ethanol productionprocess and system with front end milling method of FIG. 3A inaccordance with embodiments of the invention. In particular, each ofFIGS. 3B-3D generally depicts optional locations of the initial cookwater and optional enzyme addition, as well as the incorporation ofadditional optional solid/liquid separation steps 302, 402 and dewateredmilling steps 502, 702. Along with the additional optional solid/liquidseparations steps 302, 402, oil recovery optionally may be implementedfollowing the additional solid/liquid separation steps 302, 402. AndFIG. 3D, depicts optional front end fiber recovery. These simplifiedprocesses with their additional optional steps are discussed in greaterdetail below, and can be utilized for recovering alcohol, oil, protein,and/or fiber, with desirable yields and/or purity.

With reference now to FIG. 4, this figure depicts a flow diagram of adry grind ethanol production process and system 200 with front endmilling method in accordance with another embodiment of the inventionfor improving alcohol and/or byproduct yields, e.g., oil and/or proteinyields. To an extent, this process 200 is a variation of the dry grindethanol production process 100 with front end milling method of FIG. 3.Here, in FIG. 4, the front end milling method, which includes theliquid/solid separation step 106 and the dewatered milling step 112, issituated after the second holding tank 115 and before fermentation step111, as a way to increase oil recovery, rather than after the slurrytank 104. As a result, the feed that is sent to the oil separation step108 has a lower viscosity and a higher Brix, which is understood to makeoil recovery more efficient. In contrast, the process 100 of FIG. 3 isunderstood to increase alcohol yield by enabling a greater release ofstarch.

Due to the location of the front end milling method, as shown in FIG. 4,the feed from the slurry tank 104 is sent directly to the pre-holdingtank step 113 (instead of to the liquid/solid separation step 106 asshown in FIG. 3), whereat the slurry is subjected to one of systems A,B, or C, as discussed above. Thereafter, the slurry is sent to the firstand second holding tanks 114 and 115 to further solubilize the starchcomponent in the slurry stream.

The slurry stream from the second holding tank 115 is next subjected tothe liquid/solid separation step 106, which defines the beginning of thefront end milling method. The liquid/solid separation step 106 againseparates the liquefied solution (about 65-85% by volume), whichincludes oil, protein, and fine solids (which do not need grinding),from the heavy solids cake (about 15 to 35% by volume), which includesthe heavier fiber, grit, and germ. The now separated liquefied starchsolution can move to the optional oil separation step 108, to separateoil from the liquefied starch solution by taking advantage of densitydifferences, and an oil/emulsion/germ layer can be further forwarded tothe oil polish step 109.

The dewatered solids portion of the stream at the liquid/solidseparation step 106 (about 60 to 65% water) continues along the frontend milling method and is next subjected to the dewatered milling step112, whereat the solids, particularly the germ and grit, are reduced insize via size reduction equipment. After milling, which defines the endof the front end milling method, the solids are mixed with the liquefiedstarch solution from either the optional oil separation step 108 or fromthe liquid/solid separation step 106 to form a heavy slurry andsubjected to fermentation step 111. Also, if the emulsion and fine germparticle from the oil polish step 109 are not optionally subjected tothe solvent extraction step 110, the underflow (mainly liquefied starch)is joined up with the underflow solution from the oil separation step108, which is joined up with the solids from the dewatered milling step112 to form the heavy slurry, and sent to the fermentation step 111. Therest of the dry grind ethanol production process 200 is generally thesame as that of FIG. 3.

While not intending to be limiting, it should be further understood thatthe front end milling method also can be utilized between thepre-holding tank step 113 and the first holding tank 114, or the firstholding tank 114 and the second holding tank 115, and the like, forexample.

With reference now to FIG. 5, this figure depicts a flow diagram of adry grind ethanol production process and system 300 with front endmilling method in accordance with another embodiment of the inventionfor improving alcohol and/or byproduct yields, e.g., oil and/or proteinyields. To an extent, this process 300 is a variation of the dry grindethanol production process 100 with front end milling method of FIG. 3.In this process 300, at the front end, as compared to the process 100 ofFIG. 3, there is an additional liquid/solid separation step 302, whichis situated between the pre-holding tank step 113 and the first holdingtank 114 and is considered as an addition to the front end millingmethod. In an effort to maximize alcohol, protein, and/or oil yield,counter current washing also is set-up in this process 300 wherefiltrate, which includes liquefied starch plus middle size solids, isremoved from the slurry stream at the second liquid/solid separationstep 302. This filtrate is recycled back to mix with the ground cornflour just prior to slurry tank 104 to create a slurry and beginliquefaction, and replaces the initial cook water that is used in theembodiment shown in FIG. 3. As such, cook water now is initially addedafter the dewatered milling step 112, as compared to just after thegrinding step 102, in the process 300 of FIG. 5. This counter currentwashing set-up allows additional liquefied starch and middle size solidsto be recycled back to the dewatered milling step 112 one or more times,without the need for additional dewatered milling equipment. Therecycled liquefied starch re-visits the first liquid/solid separationstep 106 whereat it can be separated out by traveling through thescreen, then may be sent to the first holding tank 114.

With continuing reference now to FIG. 5, the feed from the slurry tank104 is subjected to the first liquid/solid separation step 106, whichdefines the beginning of the front end milling method. The liquid/solidseparation step 106 again separates the liquefied solution (about 60-80%by volume), which includes oil, protein, and fine solids (which do notneed grinding), from the heavy solids cake (about 20 to 40% by volume),which includes the heavier fiber, grit, and germ. The now separatedliquefied starch solution can move to the optional oil separation step108, to separate oil from the liquefied starch solution by takingadvantage of density differences, and then oil/emulsion/germ layer canbe further forwarded to the oil polish step 109.

The dewatered solids portion of the stream at the liquid/solidseparation step 106 (about 60 to 65% water) continues along the frontend milling method and is next subjected to the dewatered milling step112, whereat the solids, particularly the germ and grit, are reduced insize via size reduction equipment. After milling, the solids are mixedwith the cook water to form a heavy slurry and subjected to one of threeoptional pre-holding tank systems at pre-holding tank step 113, i.e.,generally one of systems A, B, and C of FIG. 2. The addition of cookwater after the dewatered milling step 112 helps with washing out andseparating liquefied starch, oil, and middle size solids.

The slurry from the pre-holding tank step 113 next is forwarded to thesecond liquid/solid separation step 302. And as with the firstliquid/solid separation step 106, the second liquid/solid separationstep 302 uses dewatering equipment, e.g., a paddle screen, a vibrationscreen, a filtration, scroll screen, or conic screen centrifuge, apressure screen, a preconcentrator, and the like, to accomplishseparation of the solids from the liquid portion. In one example, thedewatering equipment is a paddle screen or a preconcentrator, as abovedescribed. With the second liquid/solid separation step 302, the actualscreen openings may be larger in size than those in the firstliquid/solid separation step 106, which can provide higher alcohol andoil yield. In one example, the screen size used in the firstliquid/solid separation step 106 can range from 45 micron to 300 micron,and the screen size used in the second liquid/solid separation step 302can range from about 300 to 800 micron size. The filtrate, which isremoved from the second liquid/solid separating step 302 and joined upwith the ground corn flour prior to the slurry tank 104, contains about6 to 10 Brix liquefied starch solution as well as solid particles (germ,grit, and protein) having sizes smaller than the screen size openingsused in the second liquid/solid separation step 302. Using a smallerscreen at the first liquid/solid separation step 106 and a larger screenat the second liquid/solid separation step 302, the counter-currentsetup allows one to target grinding of grit and germ particles greaterthan the screen size at the first liquid/solid separation step 106 andsmaller than the screen size at the second liquid/solid separation step302. Particles larger than the screen size at the second liquid/solidseparation step 302 tend to be mostly fiber and contain less starch, sothey do not need to recycle for additional milling at the dewateredmilling step 112.

The dewatered solids portion of the stream is next forwarded, in series,to first and second holding tanks 114 and 115 for a total holding timeof about 2 to 4 hours at temperatures of about 66° C. to 85° C. tofurther solubilize the starch component in the slurry stream andcomplete liquefaction before sending to fermentation step 111. In thisprocess 300, the liquefied starch solution from the optional oilseparation step 108 and optionally the emulsion and fine germ particlefrom the oil polish step 109 can be joined up with the heavy solids fromthe second liquid/solid separation step 302 at the first holding tank114. Also, the liquefied starch solution from the first liquid/solidseparation step 106 may be combined with the solids here at the firstholding tank 114 if the optional oil separation step 108 is notutilized. The rest of the dry grind ethanol production process 300 isgenerally the same as that of FIG. 3.

The counter current washing set up in this process 300 is understood tocreate a desirable way to control the temperature, brix, pH, and enzymeconcentration profile of the slurry throughout the liquefaction process,i.e., from the slurry tank 104 to the second holding tank 115. Forexample, when the cook water and fresh enzyme, as shown in FIG. 5, areadded near the back end of liquefaction and subjected to the first andsecond holding tank steps 114, 115, the conditions of the slurry (e.g.,pH, temperature, and Brix) can be controlled by adjusting the amount ofcook water and the source of the cook water, which normally includesfresh cool well water and hot condensate from the evaporator and CO₂scrubber. These cook water sources, which have different temperatures,pH, etc., can be manipulated to provide optimum results for theliquefaction process, including helping to minimize the formation ofnonconvertible starch, and to minimize retrograded starch duringsaccharification.

In addition, the combination of the first and second liquid/solidseparation steps 106, 302 and the dewatered milling step 112 helpsprovide an additional increased yield of 1.5% alcohol, about 0.1 lb/bumore oil, and 0.5 lb/bu more protein. And the amount of back washingwater for counter current washing is only a portion of the total cookwater flow, e.g., about 50%. As such, the heavy cake content in theslurry that is subjected to the first and second holding tanks 114, 115approximately doubles, which in turn doubles the average holding timethat is necessary to give a more complete liquefaction, for example.

With reference now to FIG. 6, this figure depicts a flow diagram of adry grind ethanol production process and system 400 with front endmilling method in accordance with another embodiment of the inventionfor improving alcohol and/or byproduct yields, e.g., oil and/or proteinyields. To an extent, this process 400 is a variation of the dry grindethanol production process 300 with front end milling method of FIG. 5.Here, in FIG. 6, at the front end of the process 400, as compared to theprocess 300 of FIG. 5, there is a third liquid/solid separation step402, which is situated between the second holding tank 115 andfermentation step 111, and is considered as an addition to the front endmilling method.

As shown in FIG. 6, the feed from the slurry tank 104 is subjected tothe first liquid/solid separation step 106, which defines the beginningof the front end milling method. The first liquid/solid separation step106 again separates the liquefied solution (about 60-80% by volume),which includes oil, protein, and fine solids (which do not needgrinding), from the heavy solids cake (about 20 to 40% by volume), whichincludes the heavier fiber, grit, and germ. Rather than move to theoptional oil separation step 108 as shown in FIG. 5, the now separatedliquefied starch solution is forwarded to join up with the dewateredsolids from the second liquid/solid separation step 302. Next, thesedewatered solids are subjected to the first followed by the secondholding tanks 114, 115 for a total holding time of about 2 to 4 hours attemperatures of about 66° C. to 85° C. to further solubilize the starchcomponent in the slurry stream before sending the slurry to the thirdliquid/solid separation step 402. Various enzymes (and types thereof)such as amylase or glucoamylase, fungal, cellulose, cellobiose,protease, and the like can be optionally added to the dewatered solidsfrom the second liquid/solid separation step 302 prior to the firstholding tank 114 to enhance the separation of components, such as tohelp break the bonds between protein, starch, and fiber.

As with the first and second liquid/solid separation steps 106 and 302,the third liquid/solid separation step 402 uses dewatering equipment,e.g., a paddle screen, a vibration screen, a filtration, scroll screen,or conic screen centrifuge, a pressure screen, a pre-concentrator, andthe like, to accomplish separation of the solids from the liquidportion. In one example, the dewatering equipment is a paddle screen ora pre-concentrator, as above described. With the second liquid/solidseparation step 302, the actual screen openings may be larger in sizethan those in the first and/or third liquid/solid separation steps 106,402.

At the third liquid/solid separation step 402, the liquefied solution(about 70-85% by volume), which includes oil, protein, and fine solids,is separated from the heavy solids cake (about 15-30% by volume), whichincludes the heavier fiber, grit, and germ. The now separated liquefiedstarch solution can move to the oil separation step 108, to separate oilfrom the liquefied starch solution by taking advantage of densitydifferences, and an oil/emulsion/germ layer can be further forwarded tothe oil polish step 109. If the oil recovery centrifuge in the oilseparation step 108 is specifically a three phase decanter, the thirdliquid/solid separation step 402 may be eliminated. However, the threephase decanter performance can be improved by retaining the thirdliquid/solid separation step 402.

With further reference to FIG. 6, the underflow heavy phase and solidphase from the third liquid/solid separation step 402 can be combinedand forwarded on to join up with the liquefied starch solution from theoil separation step 108, and optionally the emulsion and fine germparticle from the oil polish step 109 and the remaining fine germparticle from the solvent extraction step 110, then directly subjectedto fermentation 111. Although not depicted in FIG. 6, if the oilseparation step 108 is not optionally utilized here, the thirdliquid/solid separation step 402 may be eliminated and the liquefiedstarch slurry solution sent directly from the second holding tank 115 tofermentation step 111. The rest of the dry grind ethanol productionprocess 300 is generally the same as that of FIG. 5.

Although not illustrated, it should be understood that the processes 300and 400 of FIG. 5 and FIG. 6, respectively, can be re-arranged so thatthe feed that goes to the oil separation step 108, for example, can besent from the pre-holding tank step 113, the first holding tank 114, orthe like. With respect to increasing alcohol yield, the process 300 inFIG. 5 is understood to be desirable for releasing more starch, whereasthe process 400 in FIG. 6 is understood to be more desirable for oilrecovery because the feed for the oil separation step 108 of FIG. 6 willhave lower viscosity and higher Brix.

With reference now to FIG. 7, this figure depicts a flow diagram of adry grind ethanol production process and system 500 with front endmilling method in accordance with another embodiment of the inventionfor improving alcohol and/or byproduct yields, e.g., oil and/or proteinyields. To an extent, this process 500 is a variation of the dry grindethanol production process 400 with front end milling method of FIG. 6.Here, in FIG. 7, at the front end of the process 500, as compared to theprocess 400 of FIG. 6, there is added a second dewatered milling step502, which is situated between the second liquid/solid separation step302 and first holding tank 114, and is considered as an addition to thefront end milling method. Thus, with this process 500, there is providedthree liquid/solid separation steps 106, 302, 402, and two dewateredmilling steps 112 and 502 in the front end milling method. It is notedthat to release starch from germ and grit particles, the particle sizeshould be smaller than about 300 to 400 micron, whereas to release oilfrom germ particles, the particle size should be smaller than about 75to 150 micron. To increase alcohol yield, while two dewatered millingsteps 112, 502 in a series are desirable, one will suffice. Yet, toincrease oil yield, two dewatered milling steps 112, 502 are desirable.

With continuing reference to FIG. 7, the dewatered solids portion of thestream at the second liquid/solid separation step 302 continues alongthe front end milling method and is subjected to the second dewateredmilling step 502, whereat the solids, particularly the germ and grit,are further reduced in size via size reduction equipment. The sizereduction equipment can include a hammer mill, a pin or impact mill, agrind mill, and the like. In one example, the size reduction equipmentis a pin mill or grind mill. This second dewatered milling step 502 isintended to further break the germ and grit particles and the bondsbetween fiber and starch, as well as oil and protein, without cuttingthe fiber too fine, thereby giving sharper separation between the fiberand protein/starch/oil. In a dewatered form, the germ and grit particlesare able to break apart more easily than the fiber as a result ofincreased rubbing action in which less fine fiber is created, but thegerm and grit are more fully milled. This results in a relativelynon-uniform particle size amongst the milled solids. For example, germand grit particles can be milled here to particle sizes between about 75to 150 microns, whereas a majority of the fiber remains within aparticle size range of 300 to 800 micron. In one example, greater than75% of the fiber remains within a particle size range of 300 to 1000micron. In another example, about 30% to about 60% by weight of thetotal particles after the second dewatered milling step 502 have aparticle size from about 100 microns to about 800 microns. In stillanother example, about 40% to about 50% by weight of the total particlesafter the second dewatered milling step 502 have a particle size fromabout 100 microns to about 800 microns. In yet another example, nogreater than 60% by weight of the total particles after the seconddewatered milling step 502 have a particle size from about 100 micronsto about 800 microns. In yet another example, no greater than 50% byweight of the total particles after the second dewatered milling step502 have a particle size from about 100 microns to about 800 microns.The rest of the dry grind ethanol production process 500 is generallythe same as that of FIG. 6.

The combination of the three liquid/solid separation steps 106, 302,402, and two dewatered milling steps 112 and 502 in the front endmilling method of FIG. 7 helps provide an additional increased yield of2% alcohol, about 0.15 lb/bu more oil, and 0.8 lb/bu more protein.

With reference now to FIG. 7A, this figure depicts a flow diagramshowing a variation of the dry grind ethanol production process andsystem 500 with front end milling method of FIG. 7 in accordance withanother embodiment of the invention for improving alcohol and/orbyproduct yields, e.g., oil and/or protein yields. In this process 500A,the counter current washing of FIG. 7, which includes removing andrecycling back the liquefied starch plus middle size solids from theslurry stream at the second liquid/solid separation step 302 so as tomix with the ground corn flour just prior to slurry tank 104, iseliminated. Instead, the ground corn flour is again mixed with initialcook water at the slurry tank 104 to create a slurry and beginliquefaction, as in FIG. 3. In turn, the filtrate from the secondliquid/solid separation step 302 is joined up with the milled solidsfrom the second dewatered milling step 502 rather than the separatedliquefied solution from the first liquid/solid separation step 106.Also, the liquefied solution from the first liquid/solid separation step106 is similarly joined up with the milled solids from the firstdewatered milling step 112. And the rest of the dry grind ethanolproduction process 500A is generally the same as that of FIG. 7.

With reference now to FIG. 7B, this figure depicts a flow diagramshowing a variation of the dry grind ethanol production process andsystem 500A with front end milling method of FIG. 7A in accordance withanother embodiment of the invention for improving alcohol and/orbyproduct yields, e.g., oil and/or protein yields. Rather thansubjecting the slurry formed from the filtrate from the secondliquid/solid separation step 302 and the milled solids from the seconddewatered milling step 502 to the first followed by the second holdingtanks 114, 115, the slurry from the first holding tank 114 is subjectedto the third liquid/solid separation step 402. Again, the thirdliquid/solid separation step 402 uses dewatering equipment to accomplishseparation of the solids from the liquid portion. The liquefied solution(about 70-85% by volume), which includes oil, protein, and fine solids,is separated from the heavy solids cake (about 15-30% by volume), whichincludes the heavier fiber, grit, and germ.

The now separated liquefied starch solution can move to the optional oilseparation step 108, and the underflow heavy phase and solid phase canbe forwarded on to join up with the liquefied starch solution from theoptional oil separation step 108, and optionally the emulsion and finegerm particle from the oil polish step 109 and the remaining fine germparticle from the solvent extraction step 110, then subjected to thesecond holding tank 115. Thereafter, the slurry is sent to and subjectedto the fermentation step 111. The total holding time in the first andsecond holding tanks is about 2 to 4 hours at temperatures of about 66°C. to 85° C. to further solubilize the starch component in the slurrystream and complete liquefaction before sending to fermentation step111. The rest of the dry grind ethanol production process 500B isgenerally the same as that of FIG. 7A.

With reference now to FIG. 8, this figure depicts a flow diagram of adry grind ethanol production process and system 600 with front endmilling method in accordance with another embodiment of the inventionfor improving alcohol and/or byproduct yields, e.g., oil and/or proteinyields. To an extent, this process 600 is a variation of the dry grindethanol production process 500 with front end milling method of FIG. 7.Here, in FIG. 8, at the front end of the process 600, as compared to theprocess 500 of FIG. 7, the liquefied solution (about 60-80% by volume)from the first liquid/solid separation step 106 is sent to the oilseparation step 108 (and an oil/emulsion/germ layer can be furtherforwarded to the oil polish step 109), rather than forwarded to join themilled solids after the second dewatered milling step 502. The dewateredsolids portion of the stream at the first liquid/solid separation step106 (about 60 to 65% water) continues along the front end milling methodand is next subjected to the first dewatered milling step 112, whereatthe solids are reduced in size via size reduction equipment.

To that end and in a further effort to maximize alcohol, protein, and/oroil yield, additional counter current washing is set-up in this process600 where filtrate, which includes liquefied starch plus middle sizesolids (2 to 6 Brix of liquefied starch solution), is removed from theslurry stream at the third liquid/solid separation step 402. Thisfiltrate, similar to the filtrate from the second liquid/solidseparation step 302, is recycled back to mix with the milled solidsafter the first dewatered milling step 112. The heavy slurry then issubjected to one of three optional pre-holding tank systems atpre-holding tank step 113, i.e., generally one of systems A, B, and C ofFIG. 2, whereat the slurry is held for about 0.5 to 1 hour holding timebefore being sent on to the second liquid/solid separation step 302. Therecycled filtrate from the third liquid/solid separation step 402replaces the cook water that is used in the process 500 of FIG. 7, whichcombines with the milled solids after first dewatered milling step 112.In view thereof, the cook water in the process 600 is now initiallyadded after the second dewatered milling step 112, along with optionalenzymes, as previously discussed. The counter current wash set-up allowsfor released oil and smaller starch/converted sugar particles to travelthrough the screens and wash forward again as larger starch particlesand grit continue to wash downstream for additional grinding andtreatment prior to fermentation. Oil recovery is understood to besuccessful because of the high concentration of sugars and oil recyclingback to the initial slurry, which mixes with the initial free oil forlater recovery. Although not depicted in FIG. 8, if the oil separationstep 108 is not optionally utilized here, the liquefied starch solutionfrom the first liquid/solid separation step 106 can be joined up withthe solids portion from the third liquid/solid separation step 402 andsent directly to fermentation step 111. The rest of the dry grindethanol production process 600 is generally the same as that of FIG. 7.

With continuing reference to FIG. 8, the screen size for theliquid/solid separation steps 106, 302, 402 can be selected so thatcertain size solid particles will be recycled back to one or more of thedewatered milling steps 112, 502 so as to be subjected to furthergrinding. For example, a 75 micron screen size may be utilized in thefirst liquid/solid separation step 106, a 150 micron screen size in thesecond liquid/solid separation step 302, and a 300 micron screen size inthe third liquid/solid separation step 402. With the counter currentwashing set up, the grit and germ particle can be selectively ground todesired particle sizes. In one example, the grit size should be lessthan about 300 micron for increased alcohol yields. In another example,the germ size should be less than about 150 micron for increased oilyields increase. In another example, the germ size should be less than45 micron for increased oil yields increase. The combination of thefirst, second, and third liquid/solid separation steps 106, 302, and 402and the first and second dewatered milling steps 112 and 502 arranged inthis counter current wash setup helps provide an additional increasedyield of 2% alcohol, about 0.15 lb/bu more oil, and 0.8 lb/bu moreprotein.

With reference now to FIG. 9, this figure depicts a flow diagram ofanother embodiment of a dry grind ethanol production process and system700 with front end milling method for improving alcohol and/or byproductyields, e.g., oil and/or protein yields. To an extent, this process 700is a variation of the dry grind ethanol production process 600 withfront end milling method of FIG. 8. Here, in FIG. 9, at the front end ofthe process 700, as compared to the process 600 of FIG. 8, there is athird dewatered milling step 702, which is situated between the thirdliquid/solid separation step 402 and the second holding tank 115, and isconsidered as an addition to the front end milling method. In addition,rather than subjecting the milled solids from the second dewateredmilling step 502 to the first followed by the second holding tanks 114,115, the slurry from the first holding tank 114 is first subjected tothe third liquid/solid separation step 402 to accomplish separation ofthe solids from the liquid portion. Also, filtrate from a fiberseparation step 704, similar to the filtrate from the secondliquid/solid separation step 302, is recycled back in a counter currentset up to mix with milled solids after the second dewatered milling step502 to form a heavy slurry. This heavy slurry is sent to the firstholding tank 114 and held for about 1 to 3 hours at a temperature ofabout 50° C. to 85° C.

Further with respect to the third liquid/solid separation step 402, theliquefied solution (about 80-90% by volume), which includes oil,protein, and fine solids, is separated from the heavy solids cake (about10-20% by volume), which includes the heavier fiber, grit, and germ. Thedewatered solids portion of the stream at the third liquid/solidseparation step 402 continues along the front end milling method and isnext subjected to the third dewatered milling step 702 whereat thesolids, particularly the germ and grit, are further reduced in size viasize reduction equipment, then subjected to the second holding tank 115.At the second holding tank 115, the slurry is mixed with filtrate (lessthan 1 Brix of liquefied starch solution) from a fiber washing anddewatering step 706 and held for about 1 to 3 hours at a temperature ofabout 50° C. to 85° C.

The size reduction equipment utilized at the third dewatered millingstep 702 can include a hammer mill, a pin or impact mill, a grind mill,and the like. In one example, the size reduction equipment is a pin millor grind mill. This third dewatered milling step 702 is intended tofurther break the germ and grit particles and the bonds between fiberand starch, as well as oil and protein, without cutting the fiber toofine, thereby giving sharper separation between the fiber andprotein/starch/oil. In a dewatered form, the germ and grit particles areable to break apart more easily than the fiber as a result of increasedrubbing action in which less fine fiber is created, but the germ andgrit are more fully milled. This results in a relatively non-uniformparticle size amongst the milled solids. For example, germ and gritparticles can be milled here to particle sizes between about 75 to 150microns, whereas a majority of the fiber remains within a particle sizerange of 300 to 800 micron. In one example, greater than 75% of thefiber remains within a particle size range of 300 to 1000 micron. Inanother example, about 30% to about 75% by weight of the total particlesafter the third dewatered milling step 702 have a particle size fromabout 100 microns to about 800 microns. In still another example, about40% to about 60% by weight of the total particles after the thirddewatered milling step 702 have a particle size from about 100 micronsto about 800 microns. In another example, no greater than 75% by weightof the total particles after the third dewatered milling step 702 have aparticle size from about 100 microns to about 800 microns. In yetanother example, no greater than 60% by weight of the total particlesafter the third dewatered milling step 702 have a particle size fromabout 100 microns to about 800 microns. In yet another example, nogreater than 50% by weight of the total particles after the thirddewatered milling step 702 have a particle size from about 100 micronsto about 800 microns.

Various enzymes (and types thereof) such as amylase or glucoamylase,fungal, cellulose, cellobiose, protease, and the like can be optionallyadded after the third dewatered milling step 702 to enhance theseparation of components, such as to help break the bonds betweenprotein, starch, and fiber within the second holding tank 115, forexample.

With continuing reference to FIG. 9, after the second holding tank 115,the slurry is sent and subjected to a fiber separation step 704, whichhelps to produce desirable fiber for secondary alcohol feed stock.Dewatering equipment, e.g., a paddle screen, vibration screen,filtration centrifuge, pressure screen, screen bowl decanter and thelike, is used at the fiber separation step 704 to accomplish separationof the fiber from the liquefied starch solution. Again, the separatedliquefied starch solution is recycled back and joins with the milledsolids from the second dewatered milling step 502 whereat the germ andgrit particles can be milled to particle sizes between about 45 to 300microns. The separated fiber portion is forwarded on, mixed with cookwater, then sent to fiber washing and dewatering step 706 whereat thefiber is washed and separated from the liquefied starch solution. Thefiber washing and dewatering step 706 can utilize dewatering equipment,e.g., a paddle screen, vibration screen, fiber centrifuge, scrollscreen, or conic screen centrifuge, pressure screen, preconcentrator,and the like, to accomplish separation of the solids from the liquidportion. In one example, the dewatering equipment is a paddle screen ora fiber centrifuge.

The washed/dewatered fiber from fiber washing and dewatering step 706can be used as feed stock for secondary alcohol production. Theresulting cellulosic material, which includes pericarp and tip cap andhas more than 35% DS, less than 10% protein, less than 2% oil, and lessthan 1% starch/sugar, can be sent to a secondary alcohol system, as isknown in the art, as feed stock without any further treatment. Thecellulose yield is about 3 lb/bu.

The underflow from oil separation step 108, and optionally the oilpolish step 109 and solvent extraction step 110, can be joined togetherand forwarded to the fermentation step 111. Although not depicted inFIG. 9, if the oil separation step 108 is not optionally utilized here,the underflow from the liquid/solid separation step 106 can be forwardeddirectly to the fermentation step 111. Because of the fiber washing anddewatering step 706 situated at the front end of the process, the sizeof the fermenter at fermentation step 111 may be decreased because it nolonger needs to accommodate the bulk of the fiber component in thestream. Thereafter, at the distillation step 118, the sugar solution isseparated from the “whole stillage”, which includes protein, oil, andgerm and grit particles and excludes fiber to a significant extent (lessthan 20% fiber), to produce alcohol. The whole stillage from thedistiller tower includes only fine fiber because the coarse fiber hasbeen removed at the fiber washing and dewatering step 706. The starchalcohol yield is about 2.82 gal/Bu, which is an increase of about 2.25%over conventional yields, due at least in part to the dewatered millingsteps 112, 502, 702 whereat starch in the grit and germ is released andeventually converted to sugar to produce more alcohol.

As further shown in FIG. 9, the back end of the process 700 can includea fine fiber/protein separation step 708, which receives the stream fromthe distillation step 118. This stream is subjected to a specialclassification decanter or fine screen pressure screen, for example, toaccomplish separation of the fine fiber from the liquid “thin stillage”portion, which includes protein. The separated fine fiber optionally canbe sent to a caustic treatment step 710 whereat the fine fiber istreated with caustic, which includes a weak alkali solution (such ascalcium, potassium, or sodium hydroxide, sodium carbonate, and thelike), to adjust the pH to about 8.5 to 9.5 and separate residual boundproteins from the fine fiber. The treated fine fiber stream is forwardedto a fine fiber washing and dewatering step 712 whereat dewateringequipment, e.g., a paddle screen, vibration screen, filtrationcentrifuge, pressure screen, screen bowl decanter and the like, is usedto accomplish separation of the fine fiber from the protein portion. Thewashed/dewatered fine fiber can be used as feed stock for secondaryalcohol production, without any further treatment. The fine fiber yieldis about 1 lb/bu, with less than 10% protein and less than 2% oil.

The filtrate from the fine fiber/protein separation step 708, whichincludes the protein, may be joined up with the residual proteinseparated at the fine fiber washing and dewatering step 712, thensubjected to similar protein recovery and drying steps like those shownin FIG. 8. Further to that end, it is noted here that the fine proteinrecovery step 130 in the process 700 of FIG. 9 is optional. In addition,the heavier components from the optional fine protein recovery step 130optionally can be subjected to centrifugation before being sent to aseparate drying step (not shown), which utilizes a dryer, e.g., a ringdryer or the like, to yield a gluten/yeast mix (protein meal) havingabout 55% protein. Also, at drying step 124, a gluten/germ/fine fibermix (protein meal) can be yielded having about 40% protein, which can becombined with the optional gluten/yeast mix (protein meal) having about55% protein to produce a mixed protein meal having about 50% proteincontent and a yield of about 5.5 to 6 lb./Bu protein meal.

The liquid overflow from the optional fine protein recovery step 130 orthe overflow from the protein recovery step 122 can move to evaporatorsat evaporation step 136 to separate any oil there from by boiling awaymoisture, leaving a thick syrup. Also, if the separated fine fiber isnot subjected to the optional caustic treatment step 710 to yieldcellulose for secondary alcohol, the centrifuged wet cake from washingand dewatering step 126 may be mixed with the syrup after evaporationstep 136 and sold as DWGS, or further dried at drying step 140 and soldas DDGS.

The high concentrated syrup (more than 60% DS) from the evaporation step136 can be used, amongst other things, as (a) nutrition for secondaryalcohol production, (b) animal feed stock, (c) plant food, (d) and/oranaerobic digestion to produce biogas. The concentrated slurryoptionally can be sent to a centrifuge, for example, to separate oilfrom the syrup at an oil recovery step. The oil can be sold as aseparate high value product. In this process, a maximum oil yield of upto 1.2 lb/bu can be produced (about 0.8 lb/bu oil yield from the frontend, and about 0.4 lb/bu oil yield from the back end). In yet anotherexample, the concentrated syrup optionally can be mixed with theresulting fine germ and protein (as well as spent yeast) recovered fromthe protein recovery step 122, then sent to drying step 124 to yield agluten/germ/yeast mix (protein meal) now including the syrup.

With reference now to FIG. 9A, this figure depicts a flow diagramshowing a variation of the dry grind ethanol production process andsystem 700 with front end milling method of FIG. 9 in accordance withanother embodiment of the invention for improving alcohol and/orbyproduct yields, e.g., oil and/or protein yields. In this process 700A,at the front end, as compared to the process 700 of FIG. 9, theliquefied solution from the third liquid/solid separation step 402optionally is sent to the oil separation step 108, rather than forwardedto join the milled solids after the first dewatered milling step 112. Inturn, the filtrate from the fiber separation step 704 is recycled backin a counter current set up to join with the milled solids from thefirst dewatered milling step 112. Also, the liquefied solution (20 to 25Brix) from the first liquid/solid separation step 106 is joined with themilled solids from the second dewatered milling step 502 and sent to thefirst holding tank 114, rather than forwarded to the optional oilseparation step 108. Although not depicted in FIG. 9A, if the oilseparation step 108 is not optionally utilized here, the liquefiedsolution from the third liquid/solid separation step 402 can be joinedtogether with the fiber portion (fiber cake) from the fiber separationstep 704 then subjected to the fermentation step 111.

With continuing reference to FIG. 9A, the fiber portion (fiber cake)from the fiber separation step 704 joins up with the heavy phase fromthe optional oil recovery step 108, and optionally the oil polish step109 and the stream from the optional solvent extraction step 110, thensubjected to the fermentation step 111. As such, the fiber washing anddewatering step 706 of FIG. 9 is eliminated. And the cook water that wasadded to the fiber portion from the fiber separation step 704 in FIG. 9is now added to the milled solids from the third dewatered milling step702 in the process 700A of FIG. 9A. The rest of the front end of theprocess 700A is generally the same as that of FIG. 9.

With further reference to FIG. 9A, the back end of the process 700A caninclude, after the distillation step 118, the whole stillage separationstep 120 whereat dewatering equipment, e.g., a paddle screen, vibrationscreen, filtration centrifuge, pressure screen, screen bowl decanter andthe like, is used to accomplish separation of the insoluble solids or“whole stillage”, which includes fiber, from the liquid “thin stillage”portion. The separated fiber optionally can be sent to caustic treatmentstep 710 whereat the fiber is treated with caustic, which includes aweak alkali solution (such as calcium, potassium, or sodium hydroxide,or sodium carbonate, and the like), to adjust the pH to about 8.5 to 9.5and separate residual bound proteins from the fiber. A high shear jetcooker or dewatered milling device may optionally be utilized in thecaustic treatment step 710.

The treated fiber stream is forwarded to a fiber/protein separation step802 whereat dewatering equipment, e.g., a paddle screen, vibrationscreen, filtration centrifuge, pressure screen, screen bowl decanter andthe like, is used to accomplish separation of the fiber from the proteinportion. The separated fiber is next subjected to a fiber washing step804, and the washed fiber can be used as feed stock for secondaryalcohol production, without any further treatment. This secondaryalcohol production from cellulose is understood to meet governmentrequirements for year 2014 for alcohol produced from starch, which mustmix 10% of alcohol produced from cellulose.

The filtrate from the fiber/protein separation step 802 and the fiberwashing step 804 is mixed together and the pH adjusted to 5 to 6 bytreating the filtrate with sulfuric acid, hydrochloric acid, phosphoricacid, or the like. The filtrate is then joined with the liquid “thinstillage” portion from the whole stillage separation step 120, andsubjected to protein recovery step 122, followed by the fine proteinrecovery step 130, like that of FIG. 9. 50% protein is realized at dryerstep 124. The centrate from the fine protein recovery step 130 is sentto evaporator 136 whereat water is removed to produce 60% DS syrup. TheDDGS dryer step 140 is eliminated in the process 700A of FIG. 9A.

With reference now to FIG. 9B, this figure depicts a flow diagramshowing a variation of the dry grind ethanol production process andsystem 700A with front end milling method of FIG. 9A in accordance withanother embodiment of the invention for improving alcohol and/orbyproduct yields, e.g., oil and/or protein yields. In this process 700B,the counter current washing of FIG. 9A, which includes removing andrecycling back within the process 700A the liquefied starch plus certainsized solids from the slurry stream at the second liquid/solidseparation step 302, the third liquid/solid separation step 402, and thefiber separation step 704, is eliminated. Instead, the ground corn flourin the process 700B is again mixed with initial cook water at the slurrytank 104 to create a slurry and begin liquefaction, as in FIG. 3. Inturn, the filtrate from the third liquid/solid separation step 402 isjoined up with the milled solids from the third dewatered milling step702 rather than forwarded to oil separation step 108.

In addition, the filtrate from the fiber separation step 704 is now sentto the oil separation step 108 rather than recycled back to join withthe milled solids from the first dewatered milling step 112. Also, thefiltrate from the second liquid/solid separation step 302 is joined upwith the milled solids from the second dewatered milling step 502 ratherthan mixed with the ground corn flour just prior to slurry tank 104. Andthe liquefied solution from the first liquid/solid separation step 106is similarly joined up with the milled solids from the first dewateredmilling step 112. Although not depicted in FIG. 9A, if the oilseparation step 108 is not optionally utilized here, the fiberseparation step 704 may be eliminated and the liquefied starch slurrysolution is sent directly from the second holding tank 115 tofermentation step 111. The rest of the dry grind ethanol productionprocess 700B is generally the same as that of FIG. 9A.

The processes of the present invention, as shown in FIGS. 3-9B caninclude, for example, up to three dewatered milling steps depending onthe desired alcohol, oil, protein, and fiber yield and purity level. Andwith the current dry mill process, the germ and grit particles stillexist after distillation and then combine together as low valuebyproduct DDGS, which includes about 30% protein, 10% oil, and 5%starch. However, the dry grind ethanol production processes, with frontend grinding method, break up the bonds between fiber, protein, oil, andstarch in the grit, germ and fiber (pericarp and tip cap) to producevaluable byproducts such as oil, protein, extra alcohol from starch andcellulose. Indeed, instead of low value DDGS, the processes of FIGS.3-9B can be used to produce desirable byproducts, including oil,protein, and cellulose.

While the present invention has been illustrated by a description ofvarious embodiments and while these embodiments have been described inconsiderable detail, it is not the intention of the applicant torestrict or in any way limit the scope of the appended claims to suchdetail. For example, although the various systems and methods describedherein have focused on corn, virtually any type of grain, including, butnot limited to, wheat, barley, sorghum, rye, rice, oats and the like,can be used. Also, for example, for the optional oil separation step108, the feed may be taken from the slurry tank 104, pre-holding tankstep 113, or from the first or second holding tank step 114, 115. Andmore broadly speaking, it should be understood that the flow diagramscan be modified, for example, to include or exclude counter currentwashing and front end oil recovery, to vary the location of thedewatered milling step(s), to produce fiber for secondary alcoholproduction (front end or back end), and to separate protein from fiberand produce high protein meal. In addition, alcohol production andrecovery can be considered to be optional steps and may be excluded fromthe process. Additional advantages and modifications will readily appearto those skilled in the art. Thus, the invention in its broader aspectsis therefore not limited to the specific details, representativeapparatus and method, and illustrative example shown and described.Accordingly, departures may be made from such details without departingfrom the spirit or scope of applicant's general inventive concept.

What is claimed is:
 1. A dry grind ethanol production process, theprocess comprising: (A) grinding dry corn kernels into corn flour; (B)mixing the ground corn flour with a liquid to produce a slurry includingfree oil, protein, starch, and fiber, germ, and grit particles; (C)subjecting the slurry of step (B) to the start of liquefaction, whichincludes adding an enzyme to the slurry; (D) after step (C), separatingthe slurry, via particle sizes alone, into a solids portion, separatelyincluding the fiber, grit, and germ particles of the slurry, and aliquid portion, including the free oil, protein, and starch of theslurry; (E) milling the separated solids portion of step (D) to reducethe size of the fiber, grit, and germ particles and release starch, oil,and protein therefrom; (F) recombining at least the starch from theseparated liquid portion of step (D) with at least the released starchof step (E) to form a second slurry; (G) converting the starches in thesecond slurry of step (F) to sugar; (H) producing alcohol from the sugarof step (G) via fermentation; and (I) recovering the alcohol afterfermentation.
 2. The process of claim 1 further comprising separatingand recovering the fiber from any of steps (A) through (I).
 3. Theprocess of claim 2, wherein the fiber of any of steps (A) through (G) isseparated and recovered prior to step (H).
 4. The process of claim 2wherein separating remaining fiber after step (H) further comprisessubjecting said remaining fiber to a caustic treatment and recoveringthe treated fiber.
 5. The process of claim 1 further comprising, priorto producing alcohol from the sugar and recovering the alcohol,separating and recovering the free oil from the liquid portion of step(D).
 6. The process of claim 5 wherein separating and recovering thefree oil from the liquid portion of step (D) includes extracting the oilfrom the liquid portion of step (D) via solvent extraction.
 7. Theprocess of claim 1 wherein said process comprises counter-currentwashing.
 8. The process of claim 1 wherein step (E) further comprisesthe following: (E1) separating the milled solids portion of step (E)into a second solids portion, including the fiber, grit, and germparticles of the milled solids portion of step (E), and a second liquidportion, including the released oil, protein, and starch of the milledsolids portion of step (E).
 9. The process of claim 8 wherein step (E1)further comprises the following: (E2) after separating the milled solidsportion of step (E) into the second solids portion and the second liquidportion, further separating the second solids portion into an additionalsolids portion, including the fiber, grit, and germ particles of thesecond solids portion, and an additional liquid portion, including thereleased oil, protein, and starch of the second solids portion.
 10. Theprocess of claim 9 further comprising separating and recovering thereleased oil from the additional liquid portion prior to producingalcohol from the sugar and recovering the alcohol.
 11. The process ofclaim 8 wherein step (E1) further comprises the following: (E3) millingthe second solids portion of step (E1) to reduce the size of the fiber,grit, and germ particles and release starch, oil, and protein therefrom.12. The process of claim 11 wherein step (E3) further comprises thefollowing: (E4) separating the milled second solids portion of step (E3)into a third solids portion, including the fiber, grit, and germparticles of the milled second solids portion of step (E3), and a thirdliquid portion, including the released oil, protein, and starch of themilled second solids portion of step (E3).
 13. The process of claim 12wherein step (E4) further comprises the following: (E5) milling thethird solids portion of step (E4) to reduce the size of the fiber, grit,and germ particles and release starch, oil, and protein therefrom. 14.The process of claim 1 further comprising separating and recovering theprotein from the liquid portion of step (D) and/or the protein from themilled solids portion of step (E).
 15. The process of claim 14 whereinthe protein from the liquid portion of step (D) and/or the protein fromthe milled solids portion of step (E) is separated and recovered afterstep (I).
 16. A dry grind ethanol production process, the processcomprising: (A) grinding dry corn kernels into corn flour; (B) mixingthe ground corn flour with a liquid to produce a slurry including freeoil, protein, starch, and fiber, germ, and grit particles; (C)subjecting the slurry of step (B) to the start of liquefaction, whichincludes adding an enzyme to the slurry; (D) after step (C), separatingthe slurry, via particle sizes alone, into a solids portion, separatelyincluding the fiber, grit, and germ particles of the slurry, and aliquid portion, including the free oil, protein, and starch of theslurry; (E) milling the separated solids portion of step (D) to reducethe size of the fiber, grit, and germ particles and release starch, oil,and protein therefrom; (F) separating the milled solids portion of step(E) into a second solids portion, including the fiber, grit, and germparticles of the milled solids portion of step (E), and a second liquidportion, including the released oil, protein, and starch of the milledsolids portion of step (E); (G) recombining at least the starch from theseparated liquid portion of step (D) with at least the released starchof step (E) to form a second slurry; (H) converting the starches in thesecond slurry of step (G) to sugar; (I) producing alcohol from the sugarof step (H) via fermentation; (J) recovering the alcohol afterfermentation; (K) grinding a second portion of dry corn kernels into asecond corn flour; (L) mixing the second corn flour with the secondliquid portion of step (F) to produce a third slurry including free oil,protein, starch, and fiber, germ, and grit particles; (M) subjecting thethird slurry of step (L) to the start of liquefaction, which includesadding an enzyme to the third slurry; (N) after step (M), separating thethird slurry, via particle sizes alone, into a third solids portion,separately including the fiber, grit, and germ particles of the thirdslurry, and a third liquid portion, including the free oil, protein, andstarch of the third slurry; (O) milling the separated third solidsportion of step (N) to reduce the size of the fiber, grit, and germparticles and release starch, oil, and protein therefrom; (P)recombining at least the starch from the separated third liquid portionof step (N) with at least the released starch of step (O) to form afourth slurry; (Q) converting the starches in the fourth slurry of step(P) to sugar; (R) producing alcohol from the sugar of step (Q) viafermentation; (S) recovering the alcohol after fermentation.
 17. Theprocess of claim 1, wherein the alcohol is ethanol.
 18. The process ofclaim 16, wherein the alcohol is ethanol.